Methods and apparatus for supplying power to touch input devices in a touch sensing system

ABSTRACT

A method and apparatus for transmitting power to active touch stimulating devices associated with a touch sensing apparatus. In this invention four methods of providing power supply to the touch-input device are presented. These methods are: EM induction transmission using a single loop antenna, EM induction transmission using a conductive layer, acoustic transmission through air, and acoustic transmission through an acoustic conductive layer.

REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part of application Ser.No. 09/670,620, filed Sep. 26, 2000, for which priority is claimed.

BACKGROUND OF THE INVENTION

[0002] Generally speaking a touch-sensing system, including a digitizer,writing panel, etc, consists of two major parts, namely thetouch-sensing tablet and the touch-input devices. The touch-inputdevices, such as a pen, a stylus, a human finger, a mouse, etc, are usedto introduce the touch events. The touch-sensing surface is used tosense the relative position of the touch-input devices on its surface.

[0003] A touch-input device can be classified as an active device or apassive device according to whether it emits an excitation signal forthe touch-sensing tablet to detect its position. For an active devicethat emits an excitation signal, a circuit to generate this signal and amethod of supplying power to this circuit are needed.

[0004] Typical methods in current touch-screen technologies to supplypower to the touch-input devices include using a battery, usingElectromagnetic (EM) induction, and Infrared induction, etc. To supplypower to the touch-input device through EM induction, the touch-sensingtablet first generates an EM field across its sensing surface toestablish an energy field. When a touch-input device is placed withinthis EM field, its couples the energy of this EM field through a coilantenna and feeds this energy into an electrical power supply for itsactive circuit.

[0005] In U.S. Pat. Nos. 5,693,914, 5,594,215, and other similarpatents, power supply methods incorporating EM induction in touchsystems used as digitizers are disclosed. The touch systems use a 2-Dantenna array to introduce the EM field onto the touch-sensing surface.This 2-D array consists of a rectangular loop antennae placed with agiven interval in both X and Y directions of the touch sensing surface.In some patent disclosures some power control methods are introduced sothat the loop antennae that are closest to the touch-input device aregiven maximum power, so that the resulting EM field distributes maximumenergy to the space near the touch-input device.

[0006] This antenna configuration has many drawbacks, one of them beingthat these loop antennae must be placed underneath the touch-sensingsurface so that enough power of the energy field can be introduced tothe device. This placement may pose a significant problem in a computertouch screen application, where combining the screen surface and theloop antenna array together is a difficult engineering problem. And itis impossible for this touch-sensing assembly to be built separately, asmost touch-screen assemblies are manufactured currently, and integratedwith the existing computer systems.

[0007] Another drawback is that, as multiple loop antennae are used togenerate the EM field, EM fields from these loop antennae couldinterfere with each other, providing a resulting EM field with pooruniformity and poor directivity. When the touch-input device is expectedto couple with this EM field using its coil antenna with strongdirectivity, the coupling result may be degraded.

SUMMARY OF THE INVENTION

[0008] The present invention generally comprises a method and apparatusfor transmitting power to active touch stimulating devices associatedwith a touch sensing apparatus. In this invention four methods ofproviding power supply to the touch-input device are presented. Thesemethods are

[0009] 1) EM induction transmission using a single loop antenna,

[0010] 2) EM induction transmission using a conductive layer,

[0011] 3) Acoustic transmission through air,

[0012] 4) Acoustic transmission through an acoustic conductive layer.

[0013] These methods as a whole can generally be regarded astransmitting power to the device using an energy conducting wave fieldthrough a specific propagating medium.

[0014] Method 1:

[0015] In this method a single loop antenna is provided in combinationwith the touch-sensing apparatus to generate the EM field. This loopantenna is placed on the boundary of the touch-sensing surface or area,such as a computer screen, a writing pad, the surface of a digitizer,etc. Using this loop antenna, the touch system generates an EM fieldthat is distributed across the touch-sensing surface. A touch-inputdevice, placed within the boundary of the touch sensing surface,receives power by coupling this EM field using a coil antenna built intothe touch input device.

[0016] It should be mentioned that as the area of coverage of the loopantenna in this invention is larger than a typical loop antennadescribed in the patent disclosures mentioned above, a touch-inputdevice in this invention may couple less energy than the prior artarrangements. However, in a co-pending patent application X,XXX,XXXmethods of using spread spectrum technology have been disclosed. Thesemethods enable a touch-input device to consume power in the order oftens of micro-watts, rather than the hundreds of micro-watts ormilli-watts of power used by touch-input devices without spread spectrumtechnology.

[0017] Method 2:

[0018] In this method the touch-sensing area is covered by a conductivelayer. This conductive layer may be transparent like those used incomputer touch screens of the capacitive type. The conductive layer maybe regarded as a distributed resistor in planar form. There are alsotransmitters placed at the boundary of this conductive layer. Thesetransmitters introduce an EM field propagating through this layer. ThisEM field is an AC field transmitted through the distributed resistanceof the conductive layer whereby, for any two points on the conductivelayer, there is a voltage differential between these two points.

[0019] When the EM field is established on the conductive layer, atouch-sensing device obtains power by taking the voltage between twopickup points. These two pickup points are conductive structures of thedevice itself, adapted to make contact with the conductive layer oncethe touch-input device is placed onto this layer, and wired to the powergenerating circuit to generate power supply to the touch-input device.

[0020] Method 3:

[0021] In this method the touch-sensing tablet generates an acousticfield across the touch-sensing surface or area, by using one or moreacoustic transmitters. The touch-input device within this acousticspatial field couples this acoustic energy field to an acoustictransducer and converts the acoustic vibration into electrical voltage.This transducer is termed an acoustic generator. The coupled voltage isthen regulated by a circuit to provide power to the circuit of thetouch-input device.

[0022] Method 4:

[0023] In this method the touch-sensing tablet is covered by an acousticwave conducting layer. This conductive layer may be transparent likeglass with good acoustic conductivity. Acoustic transmitters placed atthe boundary of the touch-sensing tablet are used to generate anacoustic wave field, propagating through this acoustic conductive layer.

[0024] Touch-input devices placed on the layer include acoustictransducers, similar to the transducers mentioned in Method 3 above andcontacted to the layer, to couple the acoustic energy and convert thisenergy into electrical power. This electrical power is regulated toprovide power supply to the device circuit.

BRIEF DESCRIPTION OF THE DRAWING

[0025]FIG. 1 is a schematic diagram of an EM spatial field embodiment ofthe invention for transmitting operating power to a touch stimulatingdevice of a touch sensing system.

[0026]FIG. 2 is a schematic diagram of an EM conductor embodiment of theinvention for transmitting operating power to a touch stimulating deviceof a touch sensing system.

[0027]FIG. 3 is a schematic diagram of an acoustic layer embodiment ofthe invention for transmitting operating power to a touch stimulatingdevice of a touch sensing system.

[0028]FIG. 4 is a schematic diagram of an acoustic layer embodiment ofthe invention for transmitting operating power to a touch stimulatingdevice of a touch sensing system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0029] The present invention generally comprises a method and apparatusfor transmitting power to active touch stimulating devices associatedwith a touch sensing apparatus. The operation of the touch stimulatingdevices in communicating with the touch sensing apparatus is notdescribed herein; rather, reference is made to companion copendingapplication XX/XXX,XXX for a full disclosure of these systems, which isincorporated herein by reference. In particular, attention is directedto FIGS. 7-16 and 25, and pp. 28-37 and 45-46 for descriptions of activetouch stimulating devices that employ spread spectrum signal techniquesto reduce requirements for operating power for these devices.

[0030] With regard to FIG. 1, a touch sensing system 31 includes anantenna 34 disposed at the periphery of the touch sensitive area 32, theantenna radiating EM energy at a frequency that is resonant with respectto the antennae of the active touch stimulating devices 23. The antenna34 may comprise one or more turns of wire or conductor about theperimeter of the assembly 33, or any other configuration that iseffective to localize the EM field to the touch sensitive area, and istuned to the appropriate resonant frequency by use of a capacitor 42connected in parallel therewith. The antenna 34 is powered by a controlcircuit 41. The antenna 34 transmits sufficient power to drive aplurality of active touch stimulating devices 21.

[0031] The apparatus of the invention includes at least one, andpreferably a plurality of active touch stimulating devices 21. Eachactive touch stimulating device includes a resonant antenna 23,comprised of an inductor 24 and a capacitor 26 in parallel connection toform a resonant circuit having a frequency defined by the parallel LCtime constant. The antenna 23 receives power transmitted at the resonantfrequency, and feeds the power signal to diode 27 and capacitor 28 togenerate regulated DC power to operate the active touch stimulatingdevice electronics.

[0032] The antenna 24 may comprise a coil formed of a plurality of turnsof wire or other conductor about an axis that is centered in the base orhousing of the device. Alternatively, the antenna may comprise a helicalor toroidal winding, or any other configuration about any sort of axis,providing that it is efficient at receiving the EM field from the systemantenna 34. Also, these embodiments may include self-stick basearrangements so that any or all of these devices may be releasablysecured to the screen assembly.

[0033] It is noted that in this embodiment antenna 34 transmits powerthrough free space to the antennae 23 of one or more active touchstimulating devices 21. The touch detecting portion of the system 31 mayor may not employ free space as the propagating medium for the signalstransmitted from the active devices 21.

[0034] With regard to FIG. 2, a further embodiment of the inventionincludes touch sensing system 40 that defines a touch sensing area 42. Aconductive layer 43 (film, coating, sheath, plate, panel, or lamina) isdisposed within the area 42, and may comprise a transparent layerassociated with a machine-controlled display. A plurality oftransmitters 46-49 are connected to the layer 43, and are disposed aboutthe periphery thereof. One possible arrangement is a rectangular layerwith 4 transmitters connected to the vertices of the rectangle, as shownin FIG. 2. The transmitters are operated by control circuit 51, and aredriven by an AC power signal to introduce an EM field propagatingthrough layer 43. The conductive layer comprises a distributedresistance extending in the plane of the layer 43, and the EM fieldpropagating through the layer forms an AC voltage gradient that extendsalong the layer.

[0035] The system 40 includes at least one active touch stimulatingdevice 52 that has a power supply 61 to operate the active touch signalgenerating circuit thereof. The power supply 61 includes a pair ofcontact points 53 and 54 extending from the device 52 to contact theconductive layer 43 at two points that are spaced apart on the surfaceof the conductive layer 43. Due to the spacing of the contacts 53 and54, there is a differential in the voltage picked up by the contactsfrom the two dimensional distributed field in the layer 43. The contactsare connected to parallel capacitors 56, and diode 57 in series andcapacitor 58 in parallel to generate regulated DC power at outputs 59 topower the active touch signal circuitry.

[0036] Thus whenever the device 52 is placed on the conductive layer 43it receives operating power and is ready for use. Note that the touchdetecting portion of the system 40 may or may not use the layer 43 as apropagating medium for touch activation signals from the device 52.

[0037] With regard to FIG. 3, another embodiment of the inventioncomprises a touch sensing system 71 having a touch sensing area 72. Anacoustic transmitter 74 is directed to transmit acoustic energy throughthe propagating medium 73 (in this case, air) and form an acousticspatial field within the area 72. The transmitter 74 is driven by acontrol circuit 76. The system includes at least one active touchstimulating device 77 that includes a power supply circuit 78. Thecircuit 78 includes an acoustic transducer 79 that receives energy fromthe acoustic spatial field and produces a voltage response, forming anacoustic generator. The voltage from transducer 79 is fed throughparallel capacitors 81 to diode 82 in series and capacitor 83 inparallel to produce regulated DC power at outputs 84 for the activetouch signal circuitry of the device 77.

[0038] Thus whenever the device 77 is placed within the medium 73 in thetouch sensing area 72 it receives operating power and is ready for use.Note that the touch detecting portion of the system 71 may or may notuse the air medium as a propagating medium for touch activation signalsfrom the device 77.

[0039] With regard to FIG. 4, there is shown a modification of theprevious embodiment of FIG. 3, in which similar components are accordedthe same reference numerals with a prime (′) designation. Within thetouch sensing area 72′ there is disposed a layer 86 (film, coating,sheath, plate, panel, or lamina) that is formed of a material thatconducts acoustic energy very well. For example, the conductive layer 86may be formed of transparent glass, which has good acousticconductivity. Acoustic transmitters placed at the boundary of thetouch-sensing tablet are used to generate an acoustic wave field,propagating through this acoustic conductive layer. A single acoustictransmitter 74′ may be used to generate the field, or, alternatively, aplurality of transmitters may be used, similar to the arrangement shownin FIG. 2. At least one active touch stimulating device 77′ includes apower supply 78 as shown previously, with the acoustic transducer 79being adapted to contact the layer 86 to receive acoustic energytherefrom.

[0040] Thus whenever the device 77′ is placed in contact with the layer86 in the touch sensing area 72′ it receives operating power and isready for use. Note that the touch sensing portion of the system 71 mayor may not use the acoustic conducting layer 86 as a propagating mediumfor touch activation signals from the device 77′.

[0041] In all the embodiments shown herein, the touch sensing systemsmay be combined with a display output of a computer or any electricalapparatus. The embodiments using free space or air as a propagatingmedium for the power signal do not require any component placed betweenthe display and the viewer, and the embodiments using a conductive layer(acoustic field or EM field) may use transparent layers applied,laminated, or closely adjacent to the screen of the display.

[0042] The foregoing description of the preferred embodiment of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and many modifications andvariations are possible in light of the above teaching without deviatingfrom the spirit and the scope of the invention. The embodiment describedis selected to best explain the principles of the invention and itspractical application to thereby enable others skilled in the art tobest utilize the invention in various embodiments and with variousmodifications as suited to the particular purpose contemplated. It isintended that the scope of the invention be defined by the claimsappended hereto.

1. In a touch sensing system for identifying at least one active touchstimulating device, an apparatus for powering the active touchstimulating device, comprising: a touch sensing area in which said atleast one active touch stimulating device operates; a transducerdisposed operatively associated with said touch sensing area fortransmitting a power signal to said at least one active touchstimulating devices; each of said active touch stimulating devicesincluding means for receiving said power signal and converting saidpower signal to electrical operating power for said active touchstimulating device; said transducer includes a first antenna extendingabout the perimeter of said touch sensing area, and further includingmeans for driving said first antenna to generate an EM field within saidtouch sensing area.
 2. The apparatus for powering an active touchstimulating device of claim 1, wherein said at least one touchstimulating device includes a second antenna adapted to receive powerfrom said EM field within said touch sensing area.
 3. The apparatus forpowering an active touch stimulating device of claim 2, wherein saidsecond antenna is a resonant antenna tuned to the frequency of said EMfield.
 4. The apparatus for powering an active touch stimulating deviceof claim 3, further including rectifying means connected to the outputof said resonant antenna to generate operating power for said activetouch stimulating device.
 5. The apparatus for powering an active touchstimulating device of claim 3, wherein said resonant antenna includes aninductor coil and a capacitor connected to be tuned to the frequency ofsaid EM field.
 6. The apparatus for powering an active touch stimulatingdevice of claim 4, wherein said touch stimulating device includes touchsignaling means incorporating spread spectrum signals.
 7. In a touchsensing system for identifying at least one active touch stimulatingdevice, an apparatus for powering the active touch stimulating device,comprising: a touch sensing area in which said at least one active touchstimulating device operates; a transducer operatively associated withsaid touch sensing area for transmitting a power signal to said at leastone active touch stimulating devices; each of said active touchstimulating devices including means for receiving said power signal andconverting said power signal to electrical operating power for saidactive touch stimulating device; wherein said transducer includes afirst acoustic transducer, and further including means for driving saidfirst acoustic transducer to generate an acoustic field in said touchsensing area.
 8. The apparatus for powering an active touch stimulatingdevice of claim 7, wherein said at least one touch stimulating deviceincludes a second acoustic transducer adapted to receive acoustic powerfrom said acoustic field within said touch sensing area.
 9. Theapparatus for powering an active touch stimulating device of claim 8,wherein said second acoustic transducer generates an AC power signal inresponse to receiving said acoustic field.
 10. The apparatus forpowering an active touch stimulating device of claim 9, furtherincluding rectifying means connected to the output of said secondacoustic transducer to generate operating power for said active touchstimulating device.
 11. The apparatus for powering an active touchstimulating device of claim 7, wherein said touch stimulating deviceincludes touch signaling means incorporating spread spectrum signals.12. The apparatus for powering an active touch stimulating device ofclaim 8, further including a conductive layer within said touch sensingarea, said first acoustic transducer being coupled to said conductivelayer to transmit said power signal through said conductive layer, saidsecond acoustic transducer being coupled to said conductive layer toreceive said acoustic field energy.
 13. In a touch sensing system foridentifying at least one active touch stimulating device, an apparatusfor powering the active touch stimulating device, comprising: a touchsensing area in which said at least one active touch stimulating deviceoperates; a transducer operatively associated with said touch sensingarea for transmitting a power signal to said at least one active touchstimulating devices; a conductive layer disposed within said touchsensing area, said transducer including at least one power signaltransmitter coupled to said conductive layer to generate an EM field insaid conductive layer; each of said active touch stimulating devicesincluding means for receiving said power signal and converting saidpower signal to electrical operating power for said active touchstimulating device.
 14. The apparatus for powering an active touchstimulating device of claim 13, wherein said transducer includes alleast one power signal transmitter coupled to peripheral portions ofsaid conductive layer and controlled to establish an AC voltage gradientacross said conductive layer.
 15. The apparatus for powering an activetouch stimulating device of claim 14, wherein said at least one touchstimulating device includes a pair of contact points adapted toelectrically engage said conductive layer, said pair of contact pointsbeing spaced apart to acquire a voltage differential from said voltagegradient in said conductive layer.
 16. The apparatus for powering anactive touch stimulating device of claim 15, further includingrectifying means connected to said voltage differential to generateoperating power for said active touch stimulating device.
 17. Theapparatus for powering an active touch stimulating device of claim 13,wherein said touch stimulating device includes touch signaling meansincorporating spread spectrum signals.
 18. In a touch sensing system foridentifying at least one active touch stimulating device in a touchsensing area, a method for powering the active touch stimulating device,comprising: providing a first antenna extending about the perimeter ofsaid touch sensing area, and driving said first antenna to generate anEM field within said touch sensing area; providing each of said activetouch stimulating devices with means for receiving a power signal fromsaid EM field and converting said power signal to electrical operatingpower for said active touch stimulating device.
 19. In a touch sensingsystem for identifying at least one active touch stimulating device in atouch sensing area, a method for powering the active touch stimulatingdevice, comprising: providing a conductive layer said touch sensingarea; generating an EM field in said conductive layer, said EM fieldhaving a voltage gradient across said touch sensing area; providing eachof said active touch stimulating devices with means for receiving apower signal from said EM field and converting said power signal toelectrical operating power for said active touch stimulating device. 20.The method for powering an active touch stimulating device of claim 19,further including the step of providing said at least one touchstimulating device with a pair of contacts adapted to electricallyengage said conductive layer and pick up a voltage differential fromsaid EM field in said conductive layer.
 21. The method for powering anactive touch stimulating device of claim 20, further including the stepof providing said at least one touch stimulating device with a rectifierfor receiving said voltage differential and generating DC operatingpower.
 22. In a touch sensing system for identifying at least one activetouch stimulating device in a touch sensing area, a method for poweringthe active touch stimulating device, comprising: providing a firstacoustic transducer adjacent to said touch sensing area, and drivingsaid first transducer to generate a acoustic field within said touchsensing area; providing each of said active touch stimulating deviceswith means for receiving a power signal from said acoustic field andconverting said power signal to electrical operating power for saidactive touch stimulating device.
 23. In a touch sensing system foridentifying at least one active touch stimulating device in a touchsensing area, a method for powering the active touch stimulating device,comprising: providing a conductive layer in said touch sensing area;providing a first acoustic transducer coupled to said conductive layer,and driving said first transducer to generate a acoustic field withinsaid conductive layer; providing each of said active touch stimulatingdevices with means for contacting said conductive layer and receiving apower signal from said acoustic field and converting said power signalto electrical operating power for said active touch stimulating device.